When does boat insurance kick in for medical?

My son cracked 4 teeth while wakeboarding behind our boat about a month ago and has had oral surgery to fix them. More dental work on the way. Medical and dental insurance denied coverage for it for several reasons so no help from the health insurer. Would our boat insurance's medical payment cover this accident? We have US boat insurance and pasted what it says for their medical payment on their policy.

"In the event of on-board injury, your policy includes up to $5,000 in per person, per occurrence medical coverage, and up to $25,000 for Family Members."

We are looking at about $8K in dental oral surgery bills and not sure how "on-board injuries" are interpretted in this scenario and wanted to get a feel of what to expect before I called USBoat.